Some people seem born under an unlucky star. But some stars are equally unlucky themselves. Astronomers have spotted a star in another galaxy plunging toward a giant black hole and being ripped to shreds, sparking a flare so brilliant that observers detected it from a distance of 2.1 billion light-years. By watching the flare brighten and fade, scientists have achieved the unprecedented feat of reconstructing the life story of the doomed sun.

Giant black holes occupy the centers of most large galaxies, including our own, whose central black hole is 4 million times as massive as the sun and swallows a star once every 10,000 to 100,000 years. Astronomers have recently seen black holes in several other galaxies rip stars apart. But the new drama is unique. "This is the first time where we're really seeing one of these events from start to finish," says astronomer Suvi Gezari of Johns Hopkins University in Baltimore, Maryland. "What was so spectacular was the fact that we actually could figure out what type of star was disrupted."

Astronomers first picked up a signal from the constellation Draco in May 2010, when the Pan-STARRS 1 telescope in Hawaii spotted a flare at visible and near-infrared wavelengths. The scientists calculate that the black hole's gravity had torn the star apart a month earlier by pulling harder on one side of the star than the other. As stellar debris funneled into the black hole, gravity and friction roasted the star's remains until they emitted ultraviolet radiation, which NASA's GALEX satellite detected in June. The flare peaked in July 2010, outshining all the stars in the galaxy put together, and then faded, but was still aglow a year later.

As Gezari's team reports online today in Nature, the black hole is about 3 million times more massive than our sun, slightly smaller than the Milky Way's central black hole, and marks the heart of a galaxy dimmer than our own. The black hole swallowed only about half the star, which lost a huge amount of energy by plummeting into the black hole. Because the laws of physics dictate that energy must be conserved, the rest of the star shot away from the black hole at enormous speed.

The team has also pieced together the life story of the unlucky star. Born roughly a billion years ago, it once generated energy as the sun does, converting hydrogen into helium at its core. When the core filled with helium, the star became a red giant—a helium core surrounded by a puffy outer layer of hydrogen.

But the distant sun was doomed. Gezari doesn't know whether it was born in a bad orbit or another star's gravity kicked it into one, but the star began approaching the black hole. Before its fiery demise, when the star was about as far from its nemesis as Pluto is from the sun, the black hole stripped off its hydrogen envelope. That left the star with only its helium core, which was a third of the sun's diameter and bore a quarter of its mass. When the star ventured within 50 million kilometers, slightly closer than Mercury is to the sun, the black hole tore it to pieces. Gezari and her colleagues can infer its composition because they detect helium but no hydrogen in its glowing remains.

"It's quite impressive," says astronomer Giuseppe Lodato of the University of Milan in Italy, who was not affiliated with the scientists who discovered the event. "They're able to infer quite a few details not just about the black hole, but also about the kind of star that has been disrupted."

Ironically, only in death could astronomers study the star's life: It was so distant that had it not been destroyed, no telescope could have seen it.

Sparking a flare so brilliant that observers detected it from a distance of 2.1 billion light-years.

Ok if the flare's light took 2.1 billions years to reach earth then the star has to be AT LEAST 2.1 billion years old right? THe story reports the star is only a billion years old..... Bad journalism. I'll bet he is a "warmist" too.

19
posted on 05/03/2012 6:42:29 PM PDT
by central_va
( I won't be reconstructed and I do not give a damn.)

don’t the law of physics breakdown at black hole “singularities”?
Why wouldn’t all of the star go into the black hole?
Why ain’t the black hole sucking all of the matter in from
all of the stuff in “space” which really ain’t that empty,
including the “stripped star”(no jokes here puhleeze.)

How did all these black holes start in the first place. I
always was told they bring “everything” into it’s venue over
the “event Horizon” and what’s gonna stop it? Only one star
every coupla eons...sounds strange...since the shape of
space is supposedly affected by mass, wouldn’t that cause
more stuff to be “funneled into the black hole?

Oh, well I just couldn’t master differential calculus, and
aal the other maths I would have needed to figure those things
out....

30
posted on 05/03/2012 8:17:28 PM PDT
by Getready
(Wisdom is more valuable than gold and diamonds, and harder to find.)

Ok if the flare's light took 2.1 billions years to reach earth then the star has to be AT LEAST 2.1 billion years old right? THe story reports the star is only a billion years old..... Bad journalism. I'll bet he is a "warmist" too.

Good catch! From the 4th paragraph of the ScienceNOW story:

"...the black hole is about 3 million times more massive than our sun..."

I went to the abstract linked in the 4th paragraph

:"The black hole has a mass of about two million solar masses..."

He must have been a journalism najor. You must be able to count in most of the sciences.

Because the laws of physics dictate that energy must be conserved, the rest of the star shot away from the black hole at enormous speed.

"Now there is a development I'd not heard of before. Fascinating."

Erasmus wrote: What they meant anyway was that momentum is conserved.

I was going to write that too, but I was busy with a prior comment. In physics you always have conservation of energy and conservation of momentum. Even though there's no physical contact, think of recoil from a firearm when it's shot.

Of course there is physical contact. The bullet is in the chamber touching something or else the slug would go forward and the casing would go backward. The bullet goes forward and the backward force is transferred through the casing into the firearm mechanism, some of which might be used to activate a semi auto feature and the rest going into your wrist or your shoulder.

Good thing we have ERASMUS to explain what they 'meant'. I guess 'scientists' aren't sticklers for accuracy ?

Anyway, regardless of how it is said, 'momentum is conserved' is like saying the truck moved because it has round wheels.

I would be more apt to believe that half the star was sucked into the 'black hole' and the remaining half was spinning round the vortex so fast that centrifugal force ejected it our past the Scharzhild (sp?) radius, possible at a much higher speed than it was entering.

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